The invention relates to a gas pressure regulator for a gas burner as specified in the introductory clause of the first patent claim.
Gas pressure regulators fitted upstream to gas burners are found in a great number of different designs. Gas pressure regulators that are employed in connection with gas burners operated in on-off mode must maintain a constant outlet pressure at a certain gas flow. In some cases such regulator should have an additional pilot burner and/or a lock up. Gas pressure regulators of commonly known design are well suited for such operation mode as they are able to stabilize a pre-set outlet pressure at a constant level within a certain flow range. If the connected gas burner is switched off, the outlet pressure will slightly rise and through a control diaphragm close the control valve in shut position.
Another application is the regulator""s employment in connection with a modulating gas burner. Preferably, there are two options available: A first option is to stabilize the outlet pressure at a constant value. This can be done by fitting a flow controlling devicexe2x80x94for example, a motor-actuated butterfly valvexe2x80x94downstream to gas pressure regulator, or by using a zero-pressure regulator to maintain the outlet pressure constantly at zero within a permissible variation. The required gas flow builds up depending on the negative pressure downstream to the burner head. A second option is to allow the outlet pressure to change. This can be achieved, for example, by using a so-called balanced pressure regulator by which the outlet pressure is altered through a control pressure that pressurizes the working diaphragm at its upper face (that is to say the flow is again depending on the outlet pressure), or by using an electronically modulating gas pressure regulator in which regulating is by an electric currentxe2x80x94or voltagexe2x80x94that substitutes for the control pressure.
In either case such gas pressure regulator must be able to feed the gas burner with the correct quantity of gas over the full modulating range, and during the ignition process. Gas pressure regulators have the disadvantage that theyxe2x80x94especially when operated at small flow rates compared with the maximum permissible flow ratexe2x80x94tend to show vibrations or pumping or get stuck in a certain position. This behavior is caused by mechanical friction between the final control elements. If this phenomenon occurs adjusting reproducible outlet pressure or gas flow values will be disabled. In order to enable adjusting reproducible outlet pressure or gas flow values, a bypass opening is usually employed. The disadvantage is that in this solution the gas pressure regulator has no longer any lock up characteristic.
In addition to the above, gas burners that are operated with a large modulation range can very often not get ignited under low-load condition as the quantity of gas available is not sufficient to form an explosive mixture. Usually, the gas burner is therefore fed through a separate gas tube to receive the quantity of gas required for starting. This gas tube, branching off from the gas main, requires an additional solenoid vale that serves as so-called start-load valve, a regulating valve that is either fixed or can be adjusted in order to control the volume flow; and a feeder line to the gas burner.
The most disadvantageous feature in this solution is that a separate gas tube must be laid what is not only expensive but also creates additional space requirements. Furthermore, there are several additional connections the gasproofness of which must be secured to the environment.
There is known another solution in which the start-load valve is fixed to a balanced pressure regulator so that laying of a separate gas tubing is no longer required. The start-load valve is connected to the balanced pressure regulator""s casing by two screws. Said screws both have a longitudinal dead-end bore hole and, for the part protruding inside the balanced pressure regulator""s casing, a lateral bore hole; they are screwed into the measuring terminals provided at both the input and output side of the balanced pressure regulator, and this way they serve to control the inflow and outflow of gas. Also in this solution, the gas through-flow is cut off by a solenoid valve of known design. An adjustable aperture provides an additional option to control the volume flow.
Also this solution has the disadvantage that there exist several additional connections the gasproofness of which must be secured to the environment. Moreover, the internal pressure drop is rather high due to the fact that the gas stream must be deviated repeatedly. In addition, the high number of pieces entails high manufacturing expenses. Finally, the distance usable for displacements (for making adjustments) is relatively short which causes the setting accuracy to be inadequate.
The invention is focusing on the issue of developing a gas pressure regulator of the said kind in which the disadvantages of the prior art described herein above are eliminated. This applies in particular to the opportunity of having a reproducible outlet pressure, or through flow, maintained throughout the entire regulating range together with the option to keep said lock up characteristic active. Also, gas burners operating with a large modulating range shall be able to get ignited. Furthermore, the internal pressure drop shall be kept as low as possible. Finally, manufacturing expenses and number of gasproof connections shall be kept at a minimum.
According to the present invention the problem is solved by providing one or more separate openings that connect the inlet-side chamber and the outlet-side chamber in addition to the existing passage that is used for pressure regulating purposes, with each of such opening being provided with a seat for a closing body that is individually assigned to said opening and guided in axial direction to its seat, whereat each closing body is connected to the armature of a solenoid valve assigned to it.
Thus a solution has been found that removes the existing disadvantages of the prior art as described herein above. Further distinguishing features of this solution are above all its simplicity and small production dimensions.
The invention comes with an advantageous arrangement if the gas pressure regulator""s casing and the solenoid valve""s casing are provided in a single-piece design by which the number of gasproof connections can be further reduced.
In addition, the armature""s longitudinal length of stroke can be adjusted so that adjusting the volume flow that is required for the ignition of the gas burner becomes easy.
Another advantageous arrangement of the invention results from the replaceable seat construction. Thus, adjustments to different through flow ranges are possible in a simple manner.
Should, for example, the low-load or start-load conditions be within the non-reproducible regulating range as described herein above this phenomenon can be eliminated by employing a gas pressure regulator of this type with the gas pressure regulator""s regulating valve being kept in shut position as long as the gas volume is small enough to possibly cause vibrations. If the gas volume is rising toward the required level, the regulating valve will open to such extent that a reliable and vibration-free regulating is allowed.
If the gas burner is ignited under low-load condition, also the lock up characteristic of the gas pressure regulator remains active. This is achieved even when the gas burner is ignited under start-load condition where said start-load is smaller than the low-load and only the low-load is failing within the critical regulating range.
If, in contrast to the above, both start-load and low-load are falling within the critical regulating range use may be made of a gas pressure regulator that has two separate openings that are controlled by two separate solenoid valves. After igniting the gas burner, the second solenoid valve opens to supply the required small-load volume. Even in this case the lock up characteristic of the gas pressure regulator remains active.
The gas pressure regulator""s design option with two separate openings, controlled by two separate solenoid valves, is used also in applications where the gas burner is ignited under start-load condition where said start-load is greater than the low-load. For controlling the ignition process the first solenoid valve is switched on and increases the gas quantity until ignition is completed, after which said solenoid valve is closed in shut position. The low-load quantity is supplied through the second solenoid valve, which means that the lock up characteristic of the gas pressure regulator remains active even under such condition.